This invention relates to semiconductor devices and methods of manufacture, and more particularly to implanted polysilicon resistor devices made by processes included in manufacture of electrically programmable memory devices.
In U.S. Pat. No. 4,110,776 issued to Rao, Stanczak, Lien and Bhatia, assigned to Texas Instruments, an implanted polycrystalline silicon resistor is disclosed. Similarly, implanted resistors in second-level polysilicon are disclosed in application Ser. No. 801,699, filed May 31, 1977, now U.S. Pat. No. 4,209,716 to J. H. Raymond, assigned to Texas Instruments. Resistors of this type have formed widespread use in static RAM devices.
The prior processes for forming polysilicon resistors required mask and etch sequences to be performed on the slice, in addition to the standard N-channel silicon gate single-level or double-level poly processes. Any added photoresist steps such as this will cause additional costs, and also reduce yields.
It is the principal object of this invention to provide an improved method of making resistors in integrated circuits, and an improved resistor made by such method. Another object is to provide a device of reduced cell size. An additional object is to provide resistors along with an array of FAMOS cells, made by a more efficient method. A further object is to provide a method of forming implanted polysilicon resistors while using N-channel double-level polysilicon processes such as used for making EPROM arrays.